1. Field of the Invention
The present invention is directed to a clutch arrangement, particularly for a motor vehicle, comprising a housing arrangement which is filled with fluid or which can be filled with fluid, at least a first friction member which is connected with the housing arrangement so as to rotate jointly therewith, at least a second friction member which is connected with a driven member or which can be connected with a driven member so as to rotate jointly therewith, wherein the friction members can be pressed against one another when at least one pressing member is acted upon by fluid.
2. Description of the Related Art
Clutch arrangements of the type mentioned above are used, for example, in the area of hydrodynamic torque converters as lockup clutches, but also as so-called wet clutches for transmission of torque in a drivetrain. In order to bring these clutches involving the use of pressure fluid into an engaged state, a piston-like pressing element is acted upon by pressure fluid and is accordingly displaced for pressing various friction surfaces against one another. The fluid pressure required for this is generally furnished by a pump provided in the area of a gear unit.
There are basically two different configurations in systems of this kind. In a so-called two-line system, the pressing piston element which divides the interior of the housing essentially into two chamber areas has an opening called a piston nozzle. The fluid is supplied under pressure to one of the chamber areas. The fluid can flow into the other chamber area via the piston nozzle by generating the pressure difference required for producing the engaged state and can be extracted from this other chamber area. An essential disadvantage of this system is the fluid leakage which exists between the two chamber areas in every state and which is even present when cooling of the system by fluid exchange is not required. In the three-line system, as it is called, a fluid exchange which is provided for cooling, for example, is carried out in the chamber area in which the frictionally contacting surfaces act to produce the torque transmission state, independent from the supply of fluid to the other chamber area. Pressure fluid is then introduced into the other chamber area, for example, for generating the pressure to be applied. Also, a permanent power loss of the pump pumping the pressure fluid is required for maintaining the torque transmission state, i.e., for maintaining the pressure difference between the two chamber areas. Other known systems work on the principle that the engagement force is supplied by a spring element, that is, e.g., a diaphragm spring or disk spring or a helical pressure spring, and that the force required for disengagement is to be provided by applied pressure. Besides the fact that the engaging forces required for producing the torque transmission state can often not be supplied by conventionally constructed diaphragm springs or helical pressure springs, a permanent operation of the pump is required in this arrangement in the disengaged state, also.
It is the object of the present invention to provide a clutch arrangement, particularly for a motor vehicle, in which it can be ensured in a simple and reliable manner that the application of pressure required for achieving and maintaining a determined clutch state can be provided.
According to the present invention, the clutch arrangement has a pressure storage arrangement which is associated with the at least one pressing member and which is in a pressure storage state or can be brought into a pressure storage state when the at least one pressing member is acted upon by pressure fluid and acts upon the pressing member with the stored pressure.
Thus, according to the principles of the present invention, when the application of pressure is initiated a pressure storage is also charged at the same time and then also acts upon the at least one pressing member and accordingly ensures that the pressing member is acted upon with sufficient force for generating the frictional connection regardless of whether or not fluid pressure continues to be supplied by a pump.
It may be provided, for example, that the pressure storage arrangement has at least one pressure storage piston element which can be displaced against the action of a force accumulator when acted upon by pressure. The force accumulator is preferably constructed in the manner of a disk spring.
In an embodiment form that is particularly advantageous because of the efficient use of the available space, the at least one pressing member comprises an annular pressing piston element which surrounds the pressure storage piston element, and a seal arrangement is provided between the pressing piston element and the pressure storage piston element, which seal arrangement permits relative displacement. In this connection, it can also be provided that the at least one pressure storage piston element is constructed annularly and is preferably supported at a radial inner side so as to be tight against fluid and displaceable with respect to the housing hub.
According to another advantageous feature of the present invention, it is preferably provided that a working surface of the pressure storage piston element is smaller than a working surface of the pressing piston element. Since the pressing piston element and the pressure storage element communicate with one another for mutual transmission of pressure, an increase in the force exerted by the pressure storage piston element is achieved by means of this dimensioning. This permits the use of a comparatively weaker force accumulator acting on the pressure storage piston element while nevertheless achieving a sufficient pressing force.
In the construction of the clutch arrangement according to the invention, in order to ensure above all that the pressing pressure provided by the charging of the pressure storage is also maintained over a longer time period, it is proposed that the at least one pressing piston element, the at least one pressure storage piston element and the housing arrangement define a first fluid chamber area which essentially does not communicate in a fluid exchanging connection with a second fluid chamber area associated with the friction members.
In another advantageous feature of the present invention, a valve arrangement is associated with the first fluid chamber area, which valve arrangement can block the first fluid chamber area after pressure fluid is supplied to the latter. In this way, it can be ensured that a fluid delivery pump need not continue to be operated once the engaged state has been produced, at least for maintaining this state. In a clutch arrangement according to the invention, the engaged state can be maintained simply by closing the first fluid chamber area and by providing the pressure storage which further ensures a sufficient pressing pressure.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.